Selections for the 2009 National Recording Registry are being announced Wednesday. They must be at least 10 years old and be culturally, historically or aesthetically significant.

The combination of Cosby — an outspoken critic of profanity and violence in hip-hop culture — with work from a rapper who was shot and killed in 1996 is notable, but organizers said Tupac's "Dear Mama" was a heartfelt homage to mothers struggling with addiction and poverty.

It's also a "relatively tame" recording, and the cultural impact of hip-hop is undeniable, program coordinator Steve Leggett said. Tupac is the third rapper inducted, following Grandmaster Flash and Public Enemy.